Metallurgy



Patented Apr. 16, 1946 METALLURGY Chester E. Unger, Mishawaka, Ind.,assignor to American Foundry Equipment Company,

Mishawaka, Ind., a corporation of Delaware Application January 12, 1943,Serial No. 472,109

6 Claims.

The invention relates to metallurgy and more particularly to a methodand apparatus for manufacturing. shot or pellets in globular form.

According to the invention, shot or pellets are made by subjecting apool of molten metal to rapid vibrations in such manner as to projectthe shot or pellets out of the molten pool whence they are permitted tohave a free fall to globulize them into spherical shape while stillmolten. The molten shot or pellets may be collected in a pool of waterwhichcauses them to solidify while in the form f round balls.

According to one form of the invention, the molten metal may be pouredinto an open top crucible and this crucible subjected to vibrationsalong three axes, a vertical axi and two hori- In some cases, instead ofapplying vibrations along three axes, it is sufficient to' apply forcedvibrations along a single vertical axis only, there being sufficientvibrations induced along the other axes to obtain the desired result.

The invention further consists in the new and novel features ofoperation and the new and original arrangements and combinations ofsteps in the process hereinafter described and more particularly set forth, in the claims. I

Although the novel features which are believed metal; and

to be characteristic of this invention will be particularly pointed outin the claims appended hereto, the invention itself, as toit objects andadvantages, and the manner in which it may be carried out, may be betterunderstood by referring to the following description taken in connectionwith the accompanying drawing forming apart hereof, in which Fig. 1illustrates diagrammatically the action of vibrations along a singlehorizontal axis on a pool of molten metal;

Fig. 2 represents diagrammatically the action of two horizontal,perpendicularly disposed vibrational forces on a pool of molten metal,Figs. 1 and 2 being shown to assist in explaining the invention;

Fig. 3 illustrates diagrammatically the effect of applying vibrationalforces along the three principal axes; I

Fig. 4 illustrates diagrammatically the efiect of applyingelectromagnetic vibrational forces along a single vertical axis to apool of molten Fig, 5 illustrates the mechanical application of a singlevertical vibrational force to a pool of molten metal.

In the following description and in the claims,

various details will be identified by specific names for convenience,but they are, intended to be as generic in their application as the artwill permit.

Like reference characters denote like parts in the several figures ofthe drawing. In the drawing accompanying and forming part of thisspecification, certain specific disclosure of the invention ismade forpurposes of explanation. but it will be understood that the details maybe modified in various respects without departure from the broad aspectof the invention.

Referring now to the drawing, and more particularly to Fig. 1, thevessel or container l0 holds a bath of molten metal II and the vesselhas applied thereto vibrational forces by an electromagnet l2 in asingle horizontal direction indicated by the arrows I 3. It will be seenthat these vibrational forces cause ripples across the horizontalsurface of the bath forming traveling waves indicated by If, nowreferring to Fig. 2, a second electromagnet I5 is provided acting alonga horizontal axis at right angles to the axis I 3, additional horizontalwaves acting along the axis 6 will be provided. The action of the twohorizontal vibrating forces serves to break up the surface of the moltenbath Il into peaks indicated by II.

If, new referring to Fig. 3, an additional electromagnet I8 is providedacting along avertical axis IS, the forces applied to the peaks I! willcause them to overcome the surface tension of the liquid, and the peaksII will be caused to separate from the surface of th liquid I l formingglobules of molten metal indicated by 20. These globules 20 will beprojected upwardly forming a shower of molten globules which will beprojected upwardly and spread laterally, falling downwardly free of thecontainer, as illustrated in Figs. 4 and 5.-

In some instances, it is only necessary to apply forced vibrations tothe bath along a single axis. Both Figs. 4 and 5 show forms in whichforced vibrations are applied only along a vertical axis. In both cases,the vertical vibrations set up induced horizontal vibrations havingcomponents at right angles to each other'so that peaks will be formed onthe surface of the bath and molten globules will beejected from themolten bath in a manner similar to that described above;

Referring now to Fig. 4. the crucible is denoted by 30 and bath by 3!and the ejected globules by 32. The crucible is supported by a verticalrod shower of particles falls clear of the crucible.

These particles may be given any suitable subsequent treatment. Forexample, they may be permitted to fall freely into a pool of water tosolidify them into round metal particles or pellets. If desired, toprevent oxidation the process may becarried out in an inert ornon-oxidiz- 33 slidably mounted in'a stationary support 34 which alsoholds an electromagnet 35 operating upon an armature secured tothe rod33.

Referring now to Fig. 5, the crucible is denoted by 40, the bath by lland the molten globules by 42. Here the crucible is supported by a rodl3 slidably mounted in the support 44. For applying vertical vibrationslengthwise of rod 43, an electric motor 45 is provided driving aneccentric 48. The eccentric 46 cooperates with a strap 41 attached torod 43.

It will be understood that the natural period of the induced horizontalvibrations in Figs. 4 and 5 will depend somewhat upon the mass andelasticity of the vibratory structure, the elasticity being imparted bythe stiffness of the rod which bends laterally under the forcedvibrations applied by the driving electromagnet or electric motor.

It is desirable in all cases that the frequency of the forced vibrationsbe substantially equal to the natural period of the vibratory system,thus obtaining a condition of resonance. It will be understood that, ifdesired, each of the forced vibratory systems above described may havean elastic element, such as a spring, incorporated therewith to give anatural period closely ap-' proaching or equalling the period of forcedvibrations. In some cases the natural elasticity of the structure may besuflicient to give the proper natural period; if not, extra springs maybe added.-

The solenoids may be .of any necessary or desirable construction. Also,any sourec of alternating current of the proper frequency may be used.In one form, the solenoids may comprise coils spaced axially having anarmature disposed therebetween, which is attached to the crucible.Suitable rectifying apparatus may be connected to the source ofalternating current for impressing an electric impulse first on one coiland then on the other coil, so as to pull the armature back and forth atthe proper rate. Or, if desired, a polarized electromagnet of the typesused in telephone receivers or loud speakers, may be used.

If desired, the process may be continuous by providing a suitable feedpipe for feeding the molten metal into the bath at a rate dependin uponthat at which the molten metal is discharged from the crucible. It willbe understood that the crucible and feed pipe may be made of suitablestructural material, such as iron or steel, provided with suitablelining towithstand the high temperatures. f

The shape of the crucible is not especially critical, nor is its depth,so long as the bath has sufiicient area and depth that the side walls donot interfere with the formation of the proper wave pattern.Furthermore, it is not necessary that the crucible partake of an actualbodily movement. In case of substantial amplitude of vibration, bodilymovement of the receptacle will occur, but in some instances, thevibrations may have such small amplitude that the shock may betransmitted throughthe walls of'the receptacle to the liquid bathwithout substantial movement of the receptacle itself.

In all cases the molten globules are ejected vertically and spreadlaterally so that a great ing atmosphere.

The size or sizes of the shot or pellets formed will depend upon thefrequency or frequencies at which the bath vibrates. It is not necessarythat the forced vibrations applied along the three reference axes be ofequal frequency or in phase, although it may be desirable to have allthree vibrations of equal frequency or else multiples of the samefrequency.

The presence in the bath of more than one frequency, either natural orforced, causes different sizes of shot to be made simultaneously. Thepresence of more than one frequency may be due to a'number of causes.For example, it may be caused'by the natural periods of the vibratorymass'not being the same as those of the forced vibrations. Or, it may becaused by applying. impure forced vibrations, that is, vibr tions whichdo not correspond to pure sine waves but which have harmonics present.0: it may be caused by deliberately making the forced vibrations appliedalpng the different axes different from one another in frequency.

In any event, where different sizes of pellets are formed, they may beseparated out in any desired type of sizing machine. It has been foundthat the sizes of the shot manufactured according to the inventioncorresponds closely to the frequencies present in the bath, andvthat thevarious sizes of shot made in any one operation all lie within a limitedrange of commercial sizes.

Thus a simple and inexpensive method of mak- 40 ing shot or pellets isprovided. This method will apply to any material capable of being heatedto a liquid stage and held in a receptacle and which can be converted toasolid stage after ejection from the receptacle. Such a method isparticu-- larly applicable to metals, especially iron and steel,including the so-called hard irons, alloy irons and alloy steels. Theinvention is especially-adaptable for the manufacture of shot used inshot blast machines either of the air blast type or of the centrifugalblast type, for cleaning or removing scale or dirt from castings orforgings, for peening the surface of materials for the purpose ofincreasing their fatigue life,'or for producing a pleasing andattractive finish.

It is a comparatively simple operation to apply molten metal to thecrucible and to vibrate this crucible at a frequency or frequenciescorresponding to the size or sizes of shot desired. Great uniformity ofsize is obtained, which size may be accurately controlled by the valueof the frequency or frequencies applied.

While certain novel features of the invention have been disclosedherein, and are pointed out in the annexed claims, it will be understoodthat various omissions, substitutions and changes may bemade by thoseskilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method of producing metal pellets which comprises subjectingmolten metal contained in an open top vessel to forced verticalvibrations acting along a substantially vertical axis, said vibrationsbeing of such frequency and amplitude as to eject a shower of moltenparticles upwardly from the open top of the vessel and causing saidelected particles to have free'i'all to cause them to solidify intospherical pellets.

2. The method of producing metal pellets which comprises subjectingmolten metal con-. tained in an open top vessel to forced verticalvibrations acting along a. substantially vertical axis, causing saidforced vibrations to induce in the molten metal natural vibrations alonga plurality of horizontal axes. said vibrations being of such frequencyand amplitude as to elect upwardly a shower of molten particles from thevessel,

of the molten metal into peaks and to elect said peaks in a shower fromthe surface of the metal and thereafter permittings'aid peaks to have afree fall to freeze them into solid pellets.

4. The method of making metal pellets by 'a' :ontinuous process whichcomprises feeding molten metal on to a solid surface, while vibratingsaid surface in a direction substantially transverse to the extentthereof. in such manner as to cause molten globules to separate from themolten metal'in a direction substantially normal to the surface thereofand to fall free thereof, then causing said molten globules to-solidifyas metal pellets, and recovering said pellets.

' 5. The method of making metal particles which comprises, placing aquantity of molten metal on an imperforate surface, generating vibratoryenergy, imparting said energy to said metal by vibrating said s'u'rfaceto cause particles of the molten metal to separate from said quantityand to be thrown off in a direction substantially normal to the surfaceof the quantity of metal; and cooling said particles below theirsolidification point.

6. The method of making ferrous particles which comprises, placingmolten ferrous metal on an impervious solid surface; generatingvibratory energy, applying said vibratory energy to said solid surfacein a direction substantially normal to its extent to dispersespontaneously the molten metal into molten particles and to direct.

said particles substantially perpendicularly away from said surface; andcooling said particles below their solidification point.

CHESTER. E. UNGER.

